Experiments with air purifiers in New Delhi

Particulate pollution has important consequences for human health, and is an issue of global concern. Ambient air pollution has become a cause for alarm in India in particular because recent data suggest that ambient pollution levels in Indian cities are some of the highest in the world.

We study the number of particles between 0.5μm and 2.5μm indoors while using affordable air purifiers in the highly polluted city of Delhi. We conducted air purifier tests in December 2015 and January 2016 in a residential apartment in South Delhi. The air purifiers we tested contained high-efficiency particulate arresting filters and were two of the most affordable available. The experiment comprised six test conditions, created by crossing three filter combinations with opening and closing the door of the room every 30 minutes, or not. Data were collected using two Dylos 1700 laser particle counters, which provide minute-wise counts of particles in two size bins: 0.5μm and larger, and 2.5μm and larger. One particle counter was placed outside in ambient air, while the other particle counter was kept inside the test room.